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Lua
Type nil, boolean, number, string, function, userdata, thread, and table. Nil Nil is the type of the value nil, whose main property is to be different from any other value; it usually represents the absence of a useful value. Boolean Boolean is the type of the values false and true. Both nil and false make a condition false; any other value makes it true. Number represents both integer numbers and real (floating-point) numbers. String String represents immutable sequences of bytes.Lua is 8-bit clean: strings can contain any 8-bit value, including embedded zeros ('\0'). Lua is also encoding-agnostic; it makes no assumptions about the contents of a string. Number The type number uses two internal representations, one called integer and the other called float. Lua has explicit rules about when each representation is used, but it also converts between them automatically as needed (see §3.4.3). Therefore, the programmer may choose to mostly ignore the difference between integers and floats or to assume complete control over the representation of each number. Standard Lua uses 64-bit integers and double-precision (64-bit) floats, but you can also compile Lua so that it uses 32-bit integers and/or single-precision (32-bit) floats. The option with 32 bits for both integers and floats is particularly attractive for small machines and embedded systems. (See macro LUA_32BITS in file luaconf.h.) Function Lua can call (and manipulate) functions written in Lua and functions written in C (see §3.4.10). Both are represented by the type function. Userdata The type userdata is provided to allow arbitrary C data to be stored in Lua variables. A userdata value represents a block of raw memory. There are two kinds of userdata: full userdata, which is an object with a block of memory managed by Lua, and light userdata, which is simply a C pointer value. Userdata has no predefined operations in Lua, except assignment and identity test. By using metatables, the programmer can define operations for full userdata values (see §2.4). Userdata values cannot be created or modified in Lua, only through the C API. This guarantees the integrity of data owned by the host program. Thread The type thread represents independent threads of execution and it is used to implement coroutines (see §2.6). Lua threads are not related to operating-system threads. Lua supports coroutines on all systems, even those that do not support threads natively. Table The type table implements associative arrays, that is, arrays that can be indexed not only with numbers, but with any Lua value except nil and NaN. (Not a Number is a special numeric value used to represent undefined or unrepresentable results, such as 0/0.) Tables can be heterogeneous; that is, they can contain values of all types (except nil). Any key with value nil is not considered part of the table. Conversely, any key that is not part of a table has an associated value nil. Tables are the sole data-structuring mechanism in Lua; they can be used to represent ordinary arrays, sequences, symbol tables, sets, records, graphs, trees, etc. To represent records, Lua uses the field name as an index. The language supports this representation by providing a.name as syntactic sugar for a"name". There are several convenient ways to create tables in Lua (see §3.4.9).